1. Field of the Invention
The present invention relates to a tape cassette used for magnetic recording/reproducing apparatus such as video cassette recorders. Hereinafter, a tape cassette will be referred to as the "cassette", a magnetic tape as the "tape", and a magnetic recording/reproducing apparatus as the "apparatus".
2. Description of the Prior Art
As a first example of a known cassette, an 8 mm cassette disclosed in Japanese Laid-Open Patent Publication No. 1-320693 will be illustrated:
Referring to FIGS. 32 to 35, the illustrated 8 mm cassette, used for a video tape recorder, includes a housing 202 in which a first reel 204 and a second reel 206 are disposed. A tape 208 is carried on the first reel 204 and the second reel 206 so as to run from the former to the latter through an opening 210 formed at the front of the housing 202. A plurality of loading posts of the apparatus are maneuvered in the opening 210 so as to bring the tape into engagement with the rotary head cylinder.
In FIG. 34, the housing 202 is provided with a rotary front cover 212 which completely covers the tape 208. When the front cover 212 is rotated upwardly (in a clockwise direction in FIG. 34) around a pair of fixed pins 220, a rear cover 214 is urged and guided by and along a guide groove 228 so as to take an upward position as shown in FIG. 35. As a result, the tape 208 is exposed to the outside. The tape 208 is stretched by the loading posts (not shown) entered into the opening 210.
Under the construction described above, when the rotary front cover 212 and the rear cover 214 are opened, they take upward positions in an overlapping state as shown in FIG. 35. To accommodate the overlapping covers 212 and 214, the housing 202 must have sufficient space in the front area. The size of the space becomes unavoidably large as compared with the thickness of the housing 202 so as to allow the rotary movement of the front and rear covers 212 and 214 therein. For example, when the two covers 212 and 214 take upward positions as shown in FIG. 35, the housing 202 becomes 1.5 times as high as when they are not opened as shown in FIG. 34.
When the two covers 212 and 214 are opened, the opening 210 is covered by the rear cover 214 in the upper portion. This limits the space for accommodating the loading posts. As a result, a relatively small, low loading posts must be used. Such dimensional restriction limits the freedom of designing a tape running mechanism which inherently occupies a sufficient space for accommodating the rotary head cylinder or cylindrical head to be operated so as to enable the tape 208 to run.
There is another type of cassette which is disclosed An Japanese Patent Publication (allowed) No. 62-50910. This cassette is used for a digital audio-tape recorder, commonly called "DAT cassette", which will be described by reference to FIGS. 36 to 38:
FIG. 36 is a perspective view showing the DAT cassette turned upside down. This cassette includes a front cover 232 covering both the front part and the upper part of an opening (not shown) formed in a housing 230. The front cover 232 is rotated around a pair of fixed pins (not shown) upwardly and downwardly with respect to the housing 230. The housing 230 is provided with a slider 234 in a lower part thereof which is slidable toward and away from the front cover 232. The slider 234 covers the back surface and the side surfaces of the housing 230, and is normally loaded toward the front cover 232 by a spring. When the slider 234 is located at a position adjacent to the front cover 232, it closes the lower open portion of the opening of the housing 230 and apertures 236 produced coaxially with a first reel and a second reel. The slider 234 is provided with apertures 238 which correspond to the apertures 236 when the slider 234 is withdrawn from the front cover 232. The front cover 232 is upwardly rotated by an upward force exerting thereon when the slider 234 is withdrawn or slid away from the opening of the housing 230.
In this DAT cassette, when the front cover 232 is rotated upwardly, the front surface of the front cover 232 is projected above the top surface of the housing 230 up to the height of 1.3 times the thickness of the housing 230. The increased height is quite against the objectives of thinness and compactness achieved by this invention.
The DAT cassette is advantageous over the above-mentioned 8 mm cassette in that the cassette is protected against dust because of the complete coverage of the opening of the housing. As a whole, however, the DAT cassette has disadvantages (1) that the apparatus becomes relatively high for the reason mentioned above, and (2) that the apparatus becomes complicated because of its mechanism required to enable the slider 234 and the front cover 232 to operate independently.
Japanese Patent Publication No. 58-21350 discloses a further known cassette, which is shown in FIGS. 39 to 41. In FIG. 39, a tape 244 pulled out of a housing 242 is covered by a front cover 246. The front cover 246 is moved along guide slots 250 produced in opposite side walls of the housing 242, and is rotated upwardly or downwardly with respect to the housing 242. A slider 248 is mounted on the housing 242 so as to be slidable to and from housing 242. In accordance with the rearward movement of the slider 248 (i.e. movement toward the back surface of the housing 242), the front cover 245 is released from the slider 248, and caused to rotate downwardly by gravity. FIGS. 40 and 41 show the state where the cassette is placed in the apparatus. As shown in FIG. 40, when the cassette is mounted on a cassette holder 252, the slider 248 is automatically moved rearwardly. Once the cassette is placed on the cassette holder 252, the cassette holder 252 is rotated downwardly around a pivot 254 as shown in FIG. 41. In accordance with the rotation of the cassette holder 252 a cover opener 256 comes into engagement with the front cover 246, and as the rotation of the cassette holder 252 advances, the front cover 246 is rotated upwardly against gravity, thereby uncovering the tape 244.
Firstly, disadvantages in common with the above-mentioned three types of cassettes are that when the front cover is rotated so as to uncover the tape, the front cover is unavoidably raised above the housing, thereby increasing the height of the housing. In the case of an 8 mm cassette, the height of the housing becomes considerably increased as is evident from FIG. 35. This results from the structure in which the front cover 212 and the rear cover 214 are rotated around a pair of fixed pivots 220. In the case of the DAT cassette, as shown in FIG. 38, when the front cover 232 is upwardly rotated around fixed pins, it projects above the top surface of the housing. This also results from the structure in which the front cover 232 is rotated around fixed pivots. This necessitates the provision of a space above the housing. The same problem arises in the examples shown in FIGS. 39 to 41.
The increased height of the housing leads to the increased size of the apparatus. This is against the latest trend toward the achievement of a thin-type compact apparatus.
Secondly, each cassette mentioned above cannot afford to have a sufficient space for allowing the loading posts and other auxiliary members to maneuver. This limits the freedom of design of the apparatus, and also makes it difficult to achieve a thin-type compact apparatus.
Thirdly, each cassette has a complicated rotary mechanism of the front cover so as to protect the tape against dust end dirt. In the 8 mm cassette, it is necessary to keep the tape out of contact with the front cover and other auxiliary members. In the DAT cassette, the apparatus must be equipped with any device whereby the front cover is upwardly moved after the rearward movement of the slider. The cassette shown in FIGS. 39 to 41 must additionally have any device for enabling the slider to slide. These additional devices make the apparatus complicated.